1/*
2 * Copyright (C) 2015 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *  * Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 *  * Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in
12 *    the documentation and/or other materials provided with the
13 *    distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#include "bionic_netlink.h"
30
31#include <errno.h>
32#include <linux/netlink.h>
33#include <linux/rtnetlink.h>
34#include <string.h>
35#include <stdlib.h>
36#include <sys/socket.h>
37#include <unistd.h>
38
39#include "private/ErrnoRestorer.h"
40
41NetlinkConnection::NetlinkConnection() {
42  fd_ = -1;
43
44  // The kernel keeps packets under 8KiB (NLMSG_GOODSIZE),
45  // but that's a bit too large to go on the stack.
46  size_ = 8192;
47  data_ = new char[size_];
48}
49
50NetlinkConnection::~NetlinkConnection() {
51  ErrnoRestorer errno_restorer;
52  if (fd_ != -1) close(fd_);
53  delete[] data_;
54}
55
56bool NetlinkConnection::SendRequest(int type) {
57  // Rather than force all callers to check for the unlikely event of being
58  // unable to allocate 8KiB, check here.
59  if (data_ == nullptr) return false;
60
61  // Did we open a netlink socket yet?
62  if (fd_ == -1) {
63    fd_ = socket(PF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
64  }
65
66  // Construct and send the message.
67  struct NetlinkMessage {
68    nlmsghdr hdr;
69    rtgenmsg msg;
70  } request;
71  memset(&request, 0, sizeof(request));
72  request.hdr.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST;
73  request.hdr.nlmsg_type = type;
74  request.hdr.nlmsg_len = sizeof(request);
75  request.msg.rtgen_family = AF_UNSPEC; // All families.
76  return (TEMP_FAILURE_RETRY(send(fd_, &request, sizeof(request), 0)) == sizeof(request));
77}
78
79bool NetlinkConnection::ReadResponses(void callback(void*, nlmsghdr*), void* context) {
80  // Read through all the responses, handing interesting ones to the callback.
81  ssize_t bytes_read;
82  while ((bytes_read = TEMP_FAILURE_RETRY(recv(fd_, data_, size_, 0))) > 0) {
83    nlmsghdr* hdr = reinterpret_cast<nlmsghdr*>(data_);
84    for (; NLMSG_OK(hdr, static_cast<size_t>(bytes_read)); hdr = NLMSG_NEXT(hdr, bytes_read)) {
85      if (hdr->nlmsg_type == NLMSG_DONE) return true;
86      if (hdr->nlmsg_type == NLMSG_ERROR) return false;
87      callback(context, hdr);
88    }
89  }
90
91  // We only get here if recv fails before we see a NLMSG_DONE.
92  return false;
93}
94